PROJECT SUMMARY/ABSTRACT Heart failure is a progressive syndrome for which novel mechanistic insights are needed. Cardiac hypertrophy is known to involve activation of a fetal gene program that alters myocyte function. Recent studies from the non-cardiac field have made genome-wide analysis of nucleosome positioning and chromatin structure technically feasible. We reason that well-orchestrated chromatin remodeling events must exist to facilitate cardiac gene expression and propose that diseases like heart failure involve deranged chromatin structure at the genomic scale. The short term goal of this work is to understand the totality of proteins in the nucleus, the changes in these proteins during cardiac hypertrophy and the alterations in nucleosome positioning that occur with disease. These questions will be pursued in a clinically-relevant mouse model of pressure overload-induced cardiac hypertrophy and failure. The long term goal of this project is to integrate these concepts to understand how the changing protein makeup of the nucleus impinges on nucleosomes to alter their composition and post-translational modification leading to modified chromatin structure across the genome. Our unifying hypothesis is that hypertrophic stimuli mobilize a protein network that alters the cardiac- specific chromatin packaging that occurs during normal development, reverting the myocyte to a more fetal- like state and causing heart failure. This application leverages state-of-the-art proteomic and next generation DNA sequencing technology to conceptually advance our understanding of heart failure. The major strength of this application is innovation-we provide a novel hypothesis, supported by strong preliminary data, explaining how cardiac phenotype is reprogrammed during heart failure. Our approach will reveal discrete molecular mechanisms, but moreover, it has the potential to provide paradigm changing insights into how the cardiac proteome impinges on the genome to regulate chromatin structure and thereby cardiac phenotype. The insights gained from this work have direct relevance to the public health problem of heart failure. These studies will map the nuclear proteome and discern the role of nucleosome positioning in cardiac phenotype. This knowledge will provide a mechanistic basis for how the genome is reprogrammed with disease and help establish new paradigms for therapy.